Research Interests

Current Projects:

In recent years, dielectrophoresis has emerged as a unique and useful tool for manipulating and capturing small particles. Dielectrophoretic force arises when a non-uniform electric field acts upon permanent or induced dipoles. Insulator-based dielectrophoresis (iDEP) involves the use of insulating geometric features within a microchannel to shape an applied electric field, thus harnessing dielectrophoretic and electrokinetic forces to capture and concentrate particles of interest. Using DEP, seemingly similar cells can be differentiated based on subtle distinctions such as antigen type on erythrocytes, or not-so-subtle differences like living versus dead bacteria. We use microchannels with a graduated, repeating pattern to selectively capture bioparticles from a complex mixture.

Electrokinetic separations juxtaposed by flow fields represent a valuable tool for separating complex mixtures. A novel separations technique that can dynamically capture specific species in bulk solution from a complex mixture without molecular recognition elements is presented here. The basic premise of the new device is based on electrophoretic principles and exploits differential transport near the capillary entrance by employing a large contraction ratio and setting flow and electric field gradients opposite one another.

Immunoassays provide a valuable detection and quantification method for biological samples. This work focuses on a novel detection platform utilizing streptavidin-coated silane particles possessing an iron oxide core as a solid capture surface. The introduction of a magnetic field causes supraparticle linear structures to form, and field manipulation produces a periodic change fluorescent signal intensity that can be exploited by signal processing strategies and analyzed independently from unbound analyte.

We are working on developing a high resolution separations platform capable of distinguishing between subtle variations of proteins. The most significant part of this development includes coupling a mass spectrometer as a detector for capillary isoelectric focusing. We are exploring how this interface works and what are the capabilities of this technique.

Liposomes in Electric Fields (Electrophoresis, BioNanotubules)

The biomimetic nature of liposomes as well as their relative ease of preparation have made them ideal for a variety of application in areas such as pharmaceuticals, cosmetics, gene therapy, and bioengineering. Electric field based techniques continue to be essential for the analysis and separation of bioparticles including lipid vesicles. Complex biological and biomimetic systems exhibit a wide range of intrinsic and field-induced properties; as a result, their electrokinetic behaviors are poorly understood and predicted. Understanding and characterizing these behaviors is crucial for the development of technology involving bioparticles and electric fields. Additionally, a better understanding of electric-field induced deformation can give a significant insight of the nature of similar effects in biological environments. Our work has included the study of the electrophoretic migration of various liposome preparations using capillary electrophoresis (CE), the assessment of theoretical models describing electric field-induced migration of vesicles, and qualitative and quantitative descriptions of liposome deformation caused by electric fields. Fluorescence and bright field microscopy as well as scanning electron microscopy (SEM) have been used to demonstrate the many unique shape changes experienced by vesicles undergoing electrophoresis.

Future Directions: Future directions of this project include continuing the enhancement of electric field-based separation of liposomes as well as membrane-associated proteins in a native-like environment by incorporating them into lipid vesicles. We are also interested on further exploring the electric field-induce behavior of other biological systems and networks.

Bioaerosols

A significant fraction of atmospheric aerosol particles are either living (microorganisms) or of biological origin (dander, plant and insect debris, etc.). Humans, animals and plants constantly emit microscopic particles of cellular material and protein that can account for up to 25% of atmospheric aerosols. Target bioaerosol particles can be considered information-rich packets that carry biochemical information specific to the living organisms present in the collection settings. Our group is interested in determining the feasibility of bioaerosol fingerprinting based on current understanding of cellular debris in aerosol and arguments regarding sampling, sensitivity, separation and detection schemes.

Our current experimental work has focused on preliminary studies involving the collection and examination of bioaerosol samples from various indoor and outdoor (local and international) environments in order to relate the information obtained from the sample analysis with the corresponding collection setting

Future Directions: Identifying and Integrating appropriate sampling, separation technologies as well as pattern identification and statistical methods to maximize the information that can be obtained from the environments of bioaerosol collection.

Superhydrophobic Surfaces

Here we explore how superhydrophobic materials can be used to provide new analytical capabilities. Such materials confine water droplets allowing for unique manipulations to be performed. Previously, we have characterized droplet properties, improved performance of MALDI mass spectrometry, performed isoelectric focusing within a drop, and explored the dynamics of drop cutting.